Easy-open wrappers are increasingly widespread, especially but not exclusively in the field of food, because of their practicality from the point of view of the user and because of their low cost from the point of view of the manufacturer.
These wrappers are generally obtained by folding and sealing in various manners laminated films composed of multiple layers.
Such multilayer laminated films have regions that are preset for tearing, which form so-called “easy openings” when the wrapper is packaged.
There are various kinds of film provided with regions preset for tearing.
A first type is constituted by multilayer films comprising a first external layer made of plastic material bonded to a second underlying layer made of metallic material, generally aluminum.
The first layer has a plurality of continuous and parallel incisions, which guide the tearing process, and are obtained by laser or ultrasound treatment, and pass through all of said first layer and stop at the second layer, which as mentioned is generally made of aluminum.
However, these through incisions are detrimental to the underlying aluminum, since they expose it to the moisture of the environment and therefore to rapid deterioration, which can be fatal for the integrity of the product contained in the wrapper constituted with this first type of film.
Further, in order to achieve good laser treatment, the material in which the incisions are provided must have a good response to laser radiation, in order to prevent alterations of the nature of the layer in the melted areas from causing unwanted modifications of the properties of the film.
Likewise, a second multilayer film type is provided with regions preset for tearing that are constituted by a plurality of holes, which are likewise through holes.
Differently from the continuous incisions, the holes provide better protection of the underlying aluminum layer, but do not eliminate the problem of its exposure to the external environment and do not guide tearing in a linear fashion.
A third type of multilayer film for easy-open wrappers is also known in which the region preset for tearing is formed by a plurality of substantially parallel cuts that do not pass through completely, are mutually close and distributed in a substantially random manner.
Although these cuts, by not being through cuts, ensure protection of the underlying aluminum layer, their random distribution does not ensure that tearing proceeds along the wrapper easily or along a substantially rectilinear path.
Further, said cuts, if obtained by abrasion or mechanical punching, can entail a dangerous increase in the mechanical fragility of the material.